I have seen these at Lembeh; I call them Sumo crabs, due to the sponge suit. They are similar to Orangutan crabs, which are an Ocinopus species. To my knowledge, they are still undescribed.

Cheers,Marli

Nice name! I usually call them Sponge Leg Crabs, but I like Sumo Crab Here's some video I posted a while back of one removing the sponge off the skin it has grown out of and putting it onto it's new body :-

Wow Kaj, amazing behaviour you've captured there. Looks like he's going to be "getting dressed" for quite a long time. I wonder if he puts the bits of sponge in his mouth to remove any edible stuff, or to apply some sort of "adhesive saliva".

Thank guys. Nick, I'm not sure if crustaceans can produce saliva. My best guess (and it is just a guess) is that he picks off the sponge and then just holds it in his mouth where he can then get a better grip before placing it on his body. Occasionally he picks one bit off, puts it in his mouth, then picks another and places that in his mouth with the other, before then taking both pieces and planting them on his new skin.

I got some more footage a year or so later of one that had just completed the process and the sponge coating was all lumpy. I imagine that the sponge covering then 'repairs' itself as sponges can do, and becomes a smooth shell.

I've seen them in Lembeh too and done a lot of trawling about for an i.d. There are a number of references to them via Google as Ocinopus aranea but none of them seem particularly authentic.
That's a great video - thanks for posting it